Sound absorbing material

ABSTRACT

The invention relates to a sound absorbing material, made from a microfilament nonwoven fabric having a mass per unit area of 40 to 300 g/m 2 , in which a nonwoven fabric is made from melt-spun, drawn, multi-component endless filament having a titer of 1.5 to 5 dtex and directly laid down to form a fibrous web; and the multi-component endless filaments, optionally after prebonding, are split at least to 80% to form micro-endless filaments having a titer of 0.1 to 1.2 dtex and bonded.

[0001] The invention relates to a sound absorbing material, made from amicrofilament nonwoven fabric having a mass per unit area of 40 to 300g/m².

[0002] Paneling parts for automobile interiors, such as roof linings,which possess sound absorbing properties, are known from the documentsEuropean Patent 0 909 680 and U.S. Pat. No. 4,851,283. They are madefrom a staple fiber nonwoven fabric layer in which preferably polyesterfibers are bonded using binding fibers, and are coated with at least onefoam material layer.

[0003] Furthermore, insulating and sound absorbing materials that aremade from staple fiber nonwoven fabrics, particularly from polyesterfibers, and are bonded using mechanical as well as thermal processes,are known from the documents DE 197 26 965 and DE 197 08 188.

[0004] In the course of ever greater requirements in the automobileindustry, new demands are being made on the suppliers. For example, thepaneling parts used in the interior of the automobile are supposed todemonstrate attractive optical and sensory properties of the decor. Theparts are supposed to be capable of recycling, to possess a very highlevel of resistance to color fading especially under the effects ofblack-panel temperatures, a low tendency to become dirty, a high levelof friction wear resistance, moisture resistance, fire resistance,cleanability, and a very good capacity for deep drawing, and furthermoreto take into account the increasing requirements with regard to noiseabsorption, with the goal of increasing the comfort of automobilepassengers.

[0005] The invention has set itself the task of indicating a soundabsorbing material, as well as a method for its production, that takeinto account the stated requirements.

[0006] According to the invention, the task is accomplished by a soundabsorbing material that is made from a microfilament nonwoven fabrichaving a mass per unit area of 40 to 300 g/m², the a nonwoven fabricbeing made from a melt-spun, drawn multi-component endless filamenthaving a titer of 1.5 to 5 dtex, being directly laid up to form afibrous web, and the multi-component endless filaments, optionallyprebonded being split to micro-endless filaments having a titer of 0.1to 1.2 dtex, up to at least 80%, and bonded. The sound absorbingmaterial demonstrates a high level of specific fiber surface at acomparatively low mass per unit area, as well as high opacity. Thefineness of the filaments permits good printability and embossability,and thereby decorative structuring of the material.

[0007] Preferably, the sound absorbing material is one in which thenonwoven fabric is made from melt-spun, aerodynamically stretchedmulti-component endless filaments and directly laid up to form a fibrousweb, having a titer of 1.5 to 3 dtex, and the multi-component endlessfilaments are split to micro-endless filaments having a titer of 0.1 to0.3 dtex, up to a degree of 80% and bonded. The sound absorbing materialdemonstrates an isotropic filament distribution in the web, makingfurther processing relatively independent of the machine runningdirection and thereby very advantageous for material utilization.

[0008] Preferably, the sound absorbing material is one in which themulti-component endless filament is a bicomponent endless filament madefrom two incompatible polymers, particularly a polyester and apolyamide. Such a bicomponent endless filament demonstrates goodsplittability into micro-endless filaments and results in anadvantageous ratio of strength to mass per unit area. At the same time,the sound absorbing material according to the invention is very easy toclean and wipe down, because of the polymers used and their filamentstructure, and demonstrates a high level of friction wear resistance,i.e. it is easy to take care of.

[0009] Preferably, the sound absorbing material is one in which themulti-component endless filaments have a cross-section having anorange-like multi-segment structure, also called a “pie” structure, thesegments alternately containing one of the two incompatible polymers ineach case. In addition to this orange-like multi-segment structure ofthe multi-component endless filaments, a “side-by-side” (s/s)arrangement of the incompatible polymers in the multi-component endlessfilaments is also possible, which arrangement is preferably used for theproduction of crimped filaments. Such segment arrangements of theincompatible polymers in the multi-component endless filament haveproven to be very easy to split. The sound absorbing material possessesa good deep drawing capacity, or deformability, which is expressed inthe average strength values at a high expansion capacity andcomparatively low modulus values.

[0010] Preferably, the sound absorbing material is furthermore one inwhich at least one of the incompatible polymers forming themulti-component endless filament contains an additive, such as colorpigments, permanently acting anti-statics, flame retarding agents and/oradditives that influence the hydrophobic properties, in amounts up to 10percent by weight. Static charges can be reduced or prevented with theadditives, and the lightfastness under black-panel temperatures can beimproved. Using overdyed products, values for lightfastness underblack-panel temperatures of ≧6 have been achieved, determined accordingto DIN EN 20105-A02.

[0011] The method according to the invention, for the production of asound absorbing material, is made up of the steps that multi-componentendless filaments are spun from the melt, stretched, and directly laidup to form a web, that prebonding takes place, and that the nonwovenfabric is bonded using high-pressure fluid jets, and, at the same time,split into micro-endless filaments having a titer of 0.1 to 1.2 dtex.The sound absorbing material obtained in this way is very uniform withregard to its thickness, it demonstrates an isotropic filamentdistribution, and it possesses no tendency to delaminate.

[0012] It is advantageous if the method for the production of the soundabsorbing material is carried out in such a manner that themulti-component endless filaments are bonded and split in that thenonwoven fabric, which has been prebonded, if necessary, is impacted atleast once on each side with high-pressure water jets. As a result, thesound absorbing material demonstrates a good surface and a degree ofsplitting of the multi-component endless filaments >80%.

[0013] It is advantageous if the sound absorbing material according tothe invention is subjected to spot calendering in order to increase itsfriction wear resistance. For this purpose, the split and bondednonwoven fabric is passed through heated rollers, at least one of whichhas elevations that result in melt-bonding of the filaments to oneanother at certain points.

[0014] The sound absorbing material according to the invention is suitedfor the production of car roof linings, door paneling, column paneling,rear window shelves and/or trunk paneling, as well as wheel boxpaneling, because of its properties, such as good printability, a highlevel of friction wear resistance, as well as its good lightfastnessunder black-panel temperatures, its thermoformability in thedeep-drawing process, and its sensory properties. In this connection, itis possible to do without an additional foam material coating, withoutsuffering major losses in sound absorbing properties, if very highlevels of weight savings are a concern.

[0015] The sound absorbing material is suitable as a sound absorbingmaterial in the construction of roof linings, in the construction ofcolumn, door, and trunk linings, in the construction of dashboards, inthe area of the engine compartment and/or floor linings, the materialdemonstrating good sound absorbing values at a low mass per unit area ascompared with known materials.

[0016] In particular, the sound absorbing material is suited as a tuftcarrier for automobile carpeting, which possesses sound absorbingproperties that are at least as good as those of conventional automobilecarpeting, with a significantly lower amount of material being required,since heavy-carpet backing coatings can be eliminated.

EXAMPLE 1

[0017] A filament sheet having a mass per unit area of 138 g/m² isproduced from a side-by-side (s/s) polyester-polyamide 6.6 (PES-PA6.6)bicomponent endless filament having a titer of 2.3 dtex and a weightratio of PES/PA6.6 of 60/40, and is subjected to water-jetneedlepunching at pressures up to 230 bar, on both sides. Thebicomponent endless filaments have a titer of <1.2 dtex and a thicknessof 0.73 mm after the water-jet needlepunching process, which results insplitting of the starting filaments, at the same time. Values of 391 Nin the machine running direction and 372 N in the crosswise directionwere determined for the tear strength.

EXAMPLE 2

[0018] A filament sheet having a mass per unit area of 115 g/m² isproduced from a 16 segment (pie) polyester-polyamide 6.6 (PES-PA6.6)bicomponent endless filament having a titer of 2.4 dtex and a weightratio of PES/PA6.6 of 55/45, and is subjected to water-jetneedlepunching at pressures up to 230 bar, on both sides. Thebicomponent endless filaments have a titer of <0.15 dtex after thewater-jet needlepunching process, which results in splitting of thestarting filaments, at the same time, and a thickness of 0.48 mm after afinal smoothing process. Values of 302 N in the machine runningdirection and 303 N in the crosswise direction were determined for thetear strength.

COMPARISON EXAMPLE 1

[0019] A commercially available single-layer needlepunched nonwovenfabric made from polyester (car roof lining material) having a thicknessof approximately 1.1 mm was used.

COMPARISON EXAMPLE 2

[0020] A laminate of a knitted fabric (approximately 0.6 mm thick) and afoam material substratum (approximately 1.6 mm thick), which istypically used as a car roof lining material, was tested.

COMPARISON EXAMPLE 3

[0021] A laminate made up of a knitted fabric (approximately 0.6 mmthick) and a polyester needlepunched nonwoven fabric (approximately 1.9mm thick), which is typically used as a car roof lining material, wastested.

COMPARISON EXAMPLE 4

[0022] A laminate made up of a knitted fabric (approximately 0.6 mmthick), a foam material intermediate layer (approximately 4.4 mm thick),and a nonwoven fabric substratum (approximately 0.3 mm thick), which istypically used as a car roof lining material, was tested.

[0023] The results of the sound absorbing properties (measured in a pipeaccording to DIN 52215) at different frequencies are listed in Table 1.TABLE 1 Ex. 500 625 800 900 1000 1120 1250 1400 1600 No. Hz Hz Hz Hz HzHz Hz Hz Hz 1 6% 12% 28% 33% 39% 46% 51% 70% 2 1%  8% 24% 34% 50% 74%91% 95% 95% Cl 1%  5% 10% 12% 14% 16% 21% 29% C2 2%  6% 11% 12% 14% 16%10% 27% C3 5% 11% 20% 24% 28% 35% 38% 54% C4 5% 10% 20% 25% 30% 33% 34%71% 76%

What is claimed is:
 1. A sound absorbing material made from amicrofilament nonwoven fabric having masses per unit area of 40 to 300g/m², the nonwoven fabric being made from melt-spun, drawn,multi-component endless filament having a titer of 1.5 to 5 dtex anddirectly laid down to form a fibrous web; and the multi-componentendless filaments, optionally after prebonding, are split at least to80% to form micro-endless filaments having a titer of 0.1 to 1.2 dtexand bonded.
 2. The sound absorbing material as recited in claim 1,wherein the nonwoven fabric is made from melt-spun, aerodynamicallystretched multi-component endless filaments directly laid up to form aweb, having a titer of 1.5 to 3 dtex, and the multi-component endlessfilaments, optionally after prebonding, are split at least to 80% toform micro-endless filaments having a titer of 0.1 to 0.3 dtex, andbonded.
 3. The sound absorbing material as recited in claim 1 or 2,wherein the multi-component endless filament is a bicomponent endlessfilament made from two incompatible polymers, particularly a polyesterand a polyamide.
 4. The sound absorbing material as recited in one ofclaims 1 to 3, wherein the multi-component endless filaments have across-section having an orange-like multi-segment structure, whereby thesegments alternately contain one of the two incompatible polymers, ineach instance, and/or have a “side-by-side” structure.
 5. The soundabsorbing material as recited in one of claims 1 to 4, wherein at leastone of the incompatible polymers forming the multi-component endlessfilament contains an additive, such as color pigments, permanentlyacting anti-statics, flame retarding agents and/or additives thatinfluence the hydrophobic properties, in amounts up to 10 percent byweight.
 6. A method for the production of the sound absorbing materialaccording to one of claims 1 to 5, wherein multi-component endlessfilaments are spun from the melt, stretched, and directly laid up toform a web, that prebonding takes place, if necessary, and that thenonwoven fabric is bonded using high-pressure fluid jets, and, at thesame time, split into micro-endless filaments having a titer of 0.1 to1.2 dtex.
 7. The method as recited in claim 6, wherein themulti-component endless filaments are bonded and split in that thenonwoven fabric, which has been prebonded if necessary, is impacted atleast once on each side with high-pressure water jets.
 8. The method asrecited in claim 6 or 7, wherein the multi-component endless filamentsare dyed by spin-dyeing and/or overdyeing.
 9. The method as recited inone of claims 6 to 8, wherein the sound absorbing material isspot-calandered.
 10. The sound absorbing material as recited in one ofclaims 1 to 9, wherein it is used for the production of car rooflinings, door paneling, column paneling, rear window shelves and/ortrunk paneling, as well as wheel box paneling.
 11. The sound absorbingmaterial as recited in one of claims 1 to 9, wherein it is used as asound absorbing layer in the construction of roof linings, in theconstruction of column, door, and trunk linings, in the construction ofdashboards, in the area of the engine compartment and/or floor linings.12. The sound absorbing material as recited in one of claims 1 to 9,wherein it is used as a tuft carrier for automobile carpeting.